Incidence patterns and genetic validation of primary glaucoma subtypes among 1 million adults in China and the UK

BACKGROUND/AIMS: Primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) are distinct diseases, yet many glaucoma cases in population-based datasets lack subtype specification. We assessed incidence patterns of glaucoma subtypes in China and the UK and used genetic evidence to infer the likely subtype composition of cases recorded as unspecified glaucoma. METHODS: Incident primary glaucoma was identified from linked inpatient records in the prospective China Kadoorie Biobank (CKB; n=512 504) and UK Biobank (UKB; n=492 329) studies. Cohort-specific phenotyping algorithms defined POAG, PACG and unspecified glaucoma. Adjusted incidence rates were estimated by direct standardisation. To support subtype inference, polygenic risk scores (PRSs) were constructed using ancestry-specific genome-wide association studies, including a new East Asian PACG meta-analysis, and tested for association with glaucoma phenotypes using multivariable logistic regression. RESULTS: Over 12 years of follow-up, 1658 primary glaucoma cases were identified in CKB and 7643 in UKB. Most (>68%) cases lacked subtype specification. Incidence increased with age and was twofold higher among women for PACG in both cohorts and for unspecified glaucoma in CKB. In UKB, POAG incidence was fivefold higher among Black than White participants, with a similar but attenuated pattern for unspecified glaucoma. PRS analyses indicated that unspecified glaucoma closely aligned with PACG in CKB but was more heterogeneous in UKB. CONCLUSION: Healthcare-recorded incidence patterns for POAG and PACG were consistent with established demographic risk factors, whereas unspecified glaucoma showed differences in subtype composition between populations. Integrating epidemiological and genetic evidence improves interpretation of glaucoma phenotypes when detailed clinical information is unavailable.